Coextruded Multilayer Film with Propylene-Based Polymer Barrier Layer

ABSTRACT

The present disclosure provides a coextruded multi layer film. The coextruded multilayer film includes a core component having from 15 to 1000 alternating layers of layer A and layer B. Layer A has a thickness from 30 nm to 1000 nm and includes a propylene-based polymer having a crystallization temperature (T 1c ). Layer B includes a second polymer having a glass transition temperature (T 2g ), wherein l\ c&lt;T 2g . Layer A has an effective moisture permeability less than 0.40 g-mil/100 in 2 /day.

BACKGROUND

The present disclosure is directed to multilayer films with nanolayerstructures that provide barrier properties.

There are many applications for plastic films or sheets where improvedbarrier properties would be beneficial. For example, a film with adowngauged overall thickness, utilizing less volume to achieve a givenbarrier, can provide improved toughness and other properties via the“freed up” volume being used by polymers providing other attributes thanbarrier.

Consequently, a need exists for films with improved barrier properties.A need further exists for films that enable downgauged packaging systemswith improved barrier properties.

SUMMARY

The present disclosure is directed to coextruded multilayer films with acore component that is a nanolayer structure. The nanolayer structureprovides the multilayer film with improved barrier properties. Bycoextruding materials to form a specified nanolayer structure, films orsheets are provided having an unexpected combination of improvedmoisture barrier and improved gas barrier properties.

In an embodiment, a coextruded multilayer film is provided. Thecoextruded multilayer film includes a core component having from 15 to1000 alternating layers of layer A and layer B. Layer A has a thicknessfrom 30 nm to 1000 nm and includes a propylene-based polymer having acrystallization temperature (T₁c). Layer B includes a second polymerhaving a glass transition temperature (T₂g), wherein Tc<T₂g. Layer A hasan effective moisture permeability less than 0.40 g-mil/100in²/day (lessthan 6.2 g-mil/m²/24 hour (hr)).

In an embodiment, the second polymer is selected from a polycarbonateand a cyclic olefin polymer.

In an embodiment, the multilayer film may include one or more additionalfilm layers.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying Figure together with the following description servesto illustrate and provide a further understanding of the disclosure andits embodiments and is incorporated in and constitutes a part of thisspecification.

FIG. 1 is a schematic diagram illustrating a method of making amultilayer film or sheet structure in accordance with an embodiment ofthe present disclosure.

DEFINITIONS

“Blend”, “polymer blend” and like terms mean a composition of two ormore polymers. Such a blend may or may not be miscible. Such a blend mayor may not be phase separated. Such a blend may or may not contain oneor more domain configurations, as determined from transmission electronspectroscopy, light scattering, x-ray scattering, and any other methodknown in the art. Blends are not laminates, but one or more layers of alaminate may contain a blend.

The term “composition” and like terms mean a mixture of two or morematerials, such as a polymer which is blended with other polymers orwhich contains additives, fillers, or the like. Included in compositionsare pre-reaction, reaction and post-reaction mixtures the latter ofwhich will include reaction products and by-products as well asunreacted components of the reaction mixture and decomposition products,if any, formed from the one or more components of the pre-reaction orreaction mixture.

An “ethylene-based polymer is a polymer that contains more than 50 molepercent polymerized ethylene monomer (based on the total amount ofpolymerizable monomers) and, optionally, may contain at least onecomonomer.

As used herein, the term “film”, including when referring to a “filmlayer” in a thicker article, unless expressly having the thicknessspecified, includes any thin, flat extruded or cast thermoplasticarticle having a generally consistent and uniform thickness up to about0.254 millimeters (10 mils). “Layers” in films can be very thin, as inthe cases of nanolayers discussed in more detail below.

As used herein, the term “sheet”, unless expressly having the thicknessspecified, includes any thin, flat extruded or cast thermoplasticarticle having a generally consistent and uniform thickness greater than“film”, generally at least 0.254 millimeters thick and up to about 7.5mm (295 mils) thick. In some cases sheet is considered to have athickness of up to 6.35 mm (250 mils).

Either film or sheet, as those terms are used herein can be in the formof shapes, such as profiles, parisons, tubes, and the like, that are notnecessarily “flat” in the sense of planar but utilize A and B layersaccording to the present disclosure and have a relatively thin crosssection within the film or sheet thicknesses according to the presentdisclosure. “Interpolymer” means a polymer prepared by thepolymerization of at least two different monomers. This generic termincludes copolymers, usually employed to refer to polymers prepared fromtwo or more different monomers, and includes polymers prepared from morethan two different monomers, e.g., terpolymers, tetrapolymers, etc.

“Melting Point” (Tm) is the extrapolated onset of melting and isdetermined by DSC as set forth in the “Test Methods” section.

“Crystallization temperature” (Tc) is the extrapolated onset ofcrystallization and is determined by DSC as set forth in the “TestMethods” section.

“Glass transition temperature” (Tg) is determined from the DSC heatingcurve as set for in the “Test Methods” section.

A “nanolayer structure,” as used herein, is a multilayer structurehaving two or more layers each layer with a thickness from 1 nanometerto 900 nanometers.

An “olefin-based polymer,” as used herein is a polymer that containsmore than 50 mole percent polymerized olefin monomer (based on totalamount of polymerizable monomers), and optionally, may contain at leastone comonomer. Nonlimiting examples of olefin-based polymer includeethylene-based polymer and propylene-based polymer.

“Polymer” means a compound prepared by polymerizing monomers, whether ofthe same or a different type, that in polymerized form provide themultiple and/or repeating “units” or “mer units” that make up a polymer.The generic term polymer thus embraces the term homopolymer, usuallyemployed to refer to polymers prepared from only one type of monomer,and the term interpolymer as defined below. It also embraces all formsof interpolymers, e.g., random, block, etc. The terms “ethylene/α-olefinpolymer” and “propylene/α-olefin polymer” are indicative ofinterpolymers as described below prepared from polymerizing ethylene orpropylene respectively and one or more additional, polymerizableα-olefin monomer. It is noted that although a polymer is often referredto as being “made of” one or more specified monomers, “based on” aspecified monomer or monomer type, “containing” a specified monomercontent, or the like, in this context the term “monomer” is obviouslyunderstood to be referring to the polymerized remnant of the specifiedmonomer and not to the unpolymerized species. In general, polymersherein are referred to has being based on “units” that are thepolymerized form of a corresponding monomer.

A “propylene-based polymer” is a polymer that contains more than 50 molepercent polymerized propylene monomer (based on the total amount ofpolymerizable monomers) and, optionally, may contain at least onecomonomer.

The numerical figures and ranges here are approximate, and thus mayinclude values outside of the range unless otherwise indicated.Numerical ranges (e.g., as “X to Y”, or “X or more” or “Y or less”)include all values from and including the lower and the upper values, inincrements of one unit, provided that there is a separation of at leasttwo units between any lower value and any higher value. As an example,if a compositional, physical or other property, such as, for example,temperature, is from 100 to 1,000, then all individual values, such as100, 101, 102, etc., and sub ranges, such as 100 to 144, 155 to 170, 197to 200, etc., are expressly enumerated. For ranges containing valueswhich are less than one or containing fractional numbers greater thanone (e.g., 1.1, 1.5, etc.), one unit is considered to be 0.0001, 0.001,0.01 or 0.1, as appropriate. For ranges containing single digit numbersless than ten (e.g., 1 to 5), one unit is typically considered to be0.1. For ranges containing explicit values (e.g., 1 or 2, or 3 to 5, or6, or 7) any subrange between any two explicit values is included (e.g.,1 to 2; 2 to 6; 5 to 7; 3 to 7; 5 to 6; etc.). These are only examplesof what is specifically intended, and all possible combinations ofnumerical values between the lowest value and the highest valueenumerated, are to be considered to be expressly stated in thisdisclosure.

DETAILED DESCRIPTION

1. Solid Constraining Layer-crystalline

The present disclosure provides a multilayer film. In an embodiment, themultilayer film includes a constraining layer with a solid constrainingpolymer. A “solid constraining polymer,” as used herein is a polymerthat solidifies (or vitrifies) from a melt state to a glassy state asindicated by a glass-transition temperature, Tg.

In an embodiment, a coextruded multilayer film is provided and includesa core component. The core component includes from 15 to 1000alternating layers of layer A and layer B. Layer A has a thickness from30 nm to 1000 nm and includes a propylene-based polymer having acrystallization temperature (T₁c). Layer B has a thickness from 30 nm to1000 nm and includes a second polymer having a glass transitiontemperature (T₂g), wherein T₁c<T₂g. Layer A has an effective moisturepermeability less than 0.40 g-mil/100 in²/day (less than 6.2 g-mil/m²/24hr).

In an embodiment, layer A has an effective moisture permeability from0.1, or 0.2 to less than or equal to 0.3, or less than 0.40 g-mil/100in²/day (from 1.55, or 3.1 to less than or equal to 4.65, or less than6.2 g-mil/m²/24 hr).

A. Layer A

The core component of the present multilayer film includes from 15 to1000 alternating layers of layer A and layer B. Layer A includes apropylene-based polymer. The propylene-based polymer may be a propylenehomopolymer or a propylene/α-olefin copolymer.

In an embodiment, the propylene-based polymer is a propylenehomopolymer. The propylene homopolymer has a MFR from 0.1 g/10 min, or0.5 g/10 min, or 1.0 g/10 min, or 1.5 g/10 min, to 2.0 g/10 min, or 2.5g/10 min. The propylene homopolymer has a density from 0.85 g/cc to 0.95g/cc. The propylene homopolymer has a crystallization temperature (T₁c)less than 125° C., or from 115° C., or 118° C., or 120° C., or 122° C.to less than 125° C. The propylene homopolymer has a meltingtemperature, Tm, from 155° C., or 160° C. to 165° C., or 170° C. Thepropylene homopolymer has a crystallinity from 30%, or 35%, or 38% to40% to 45%, or 50%, or 55%, or 60%.

In an embodiment, the propylene-based polymer is a propylene/α-olefincopolymer. The α-olefin is a C₄-C₂₀ α-olefin, or a C₄-C₁₀ α-olefin. Inanother embodiment, the α-olefin is selected from the group consistingof 1-butene, 1-hexene, and 1-octene. In a further embodiment, thepropylene/α-olefin copolymer has a crystallinity from 10% to 40%.

In an embodiment, the propylene/α-olefin copolymer is apropylene/ethylene copolymer. The propylene/ethylene copolymer has a MFRfrom 0.1 g/10 min to 10 g/10 min. the propylene/ethylene copolymer has adensity from 0.85 g/cc to 0.93 g/cc.

B. Layer B

The core component of the present multilayer film includes from 15 to1000 alternating layers of layer A and layer B. Layer B has a thicknessfrom 30 nm to 1000 nm and includes a second polymer having a glasstransition temperature (T₂g). The second polymer is selected such thatthe crystallization temperature, T₁c, of the propylene-based polymer inlayer A is less than the glass transition temperature (T₂g), for thesecond polymer of layer B.

The relationship between the crystallization temperature, T₁c, for thepropylene-based polymer in layer A and the glass transition temperature,T₂g, for the second polymer in layer B is:

T₁c<T₂g

wherein T₁e and T₂g each is degrees Centigrade (° C.).

In an embodiment, T₂g-T₁c is greater than 20° C., or greater than 25°C., or greater than 30° C., or greater than 35° C., or greater than 40°C., or greater than 45° C.

In an embodiment, the second polymer for layer B is selected from apolycarbonate and a cyclic olefin polymer.

i. Polycarbonate

In an embodiment, the second polymer of layer B includes apolycarbonate. A “polycarbonate,” as used herein, is a thermoplasticresin derived from a diphenol, phosgene, and a linear polyester of acarbonic acid. The polycarbonate can be a homopolycarbonate, acopolycarbonate, or an aromatic polycarbonate.

In an embodiment, the polycarbonate is an aromatic polycarbonate. Thepreparation of aromatic polycarbonate can be carried out, for example,by reaction of a diphenol with carbonic acid halide, preferablyphosgene, and/or with aromatic dicarboxylic acid dihalide, preferablybenzenedicarboxylic acid dihalides, according to the interfacialprocess, optionally using chain terminators, for example monophenols,and optionally using branching agents having a functionality of three ormore than three, for example triphenols or tetraphenols. Preparation bya melt polymerization process by reaction of diphenols with, forexample, diphenyl carbonate is also possible.

Aromatic polycarbonates typically have mean weight-average molecularweights (M_(w), measured, for example, by GPC, ultracentrifugation orscattered light measurement) of from 10,000 to 20,000 g/mol, or from15,000 to 80,000 g/mol, or from 24,000 to 32,000 g/mol.

The aromatic polycarbonate can be branched by the incorporation of from0.05 to 2.0 mol %, based on the sum of the diphenols used, of compoundshaving a functionality of three, or more than three phenolic groups.

In an embodiment, the aromatic polycarbonate has a density from 1.0 g/ccto 2.0 g/cc, and an MFR from 15 g/10 min to 20 g/10 min.

In an embodiment, the polycarbonate is a copolycarbonate.

The copolycarbonate can be formed from bisphenol A with up to 15 mol %,based on the molar sums of diphenols,2,2-bis(3,5-dibromo-4-hydroxyphenyl)-propane. It is also possible to usefrom 1 to 25 wt. %, preferably from 2.5 to 25 wt. %, based on the totalamount of diphenols to be used, of polydiorganosiloxanes havinghydroxyaryloxy end groups.

In an embodiment, the polycarbonate is a homopolycarbonate. The diphenolis bisphenol A.

In an embodiment, the multilayer film includes layer A having apropylene homopolymer with a T₁c less than 125° C. The propylenehomopolymer has a MFR from 1.5 g/10 min to 2.5 g/10 min. Thepropylene-based polymer has a crystallinity from 35% to 60%. Layer Bincludes a polycarbonate with a T₂g greater than 125° C., or greaterthan 130° C., or greater than 135° C., or greater than 140° C., orgreater than 145° C., or greater than 150° C., or greater than 155° C.,or greater than 160° C., or greater than 170° C. In a furtherembodiment, (polycarbonate) T₂g-T₁c (propylene homopolymer) is greaterthan 40° C., or greater than 50° C.

ii. Cyclic Olefin Polymer

The core component of the present multilayer film includes from 15 to1000 alternating layers of layer A and layer B. In an embodiment, thesecond polymer of layer B includes a cyclic olefin polymer. A “cyclicolefin polymer (or “COP”) is an olefin-based polymer that includes asaturated hydrocarbon ring. Suitable COPs include at least 25 wt %cyclic units, which weight percentage is calculated based on the weightpercentage of the olefin monomer units containing, includingfunctionalized to contain, the cyclic moiety (“MCCM”) that ispolymerized into the COP as a percentage of the total weight of monomerspolymerized to form the final COP.

A “cyclic olefin polymer (or “COP”) is an olefin-based polymer thatincludes a saturated hydrocarbon ring. Suitable COPs include at least 25wt % cyclic units, which weight percentage is calculated based on theweight percentage of the olefin monomer units containing, includingfunctionalized to contain, the cyclic moiety (“MCCM”) that ispolymerized into the COP as a percentage of the total weight of monomerspolymerized to form the final COP.

In an embodiment, the COP includes at least 40 wt %, or at least 50 wt %or at least 75 wt % MCCM. The cyclic moiety can be incorporated in thebackbone of the polymer chain (such as from a norbornene ring-openingtype of polymerization) and/or pendant from the polymer backbone (suchas by polymerizing styrene (which is eventually hydrogenated to a cyclicolefin) or other vinyl-containing cyclic monomer). The COP can be ahomopolymer based on a single type of cyclic unit; a copolymercomprising more than one cyclic unit type; or a copolymer comprising oneor more cyclic unit type and other incorporated monomer units that arenot cyclic, such as units provided by or based on ethylene monomer.Within copolymers, the cyclic units and other units can be distributedin any way including randomly, alternately, in blocks or somecombination of these. The cyclic moiety in the COP need not result frompolymerization of a monomer comprising the cyclic moiety per se but mayresult from cyclicly functionalizing a polymer or other reaction toprovide the cyclic moiety units or to form the cyclic moiety from acyclic moiety precursor. As an example, styrene (which is a cyclicmoiety precursor but not a cyclic unit for purposes of this disclosure)can be polymerized to a styrene polymer (not a cyclic olefin polymer)and then later be completely or partially hydrogenated to result in aCOP.

The MCCMs which can be used in polymerization processes to providecyclic units in COP's include but are not limited to norbornene andsubstituted norbornenes. As mentioned above, cyclic hexane ring unitscan be provided by hydrogenating the styrene aromatic rings of styrenepolymers. The cyclic units can be a mono- or multi-cyclic moiety that iseither pendant to or incorporated in the olefin polymer backbone. Suchcyclic moieties/structures include cyclobutane, cyclohexane orcyclopentane, and combinations of two or more of these. For example,cyclic olefin polymers containing cyclohexane or cyclopentane moietiesare α-olefin polymers of 3-cyclohexyl-1-propene (allyl cyclohexane) andvinyl cyclohexane.

In an embodiment, the COP is a cyclic olefin block copolymers (or “CBC”)prepared by producing block copolymers of butadiene and styrene that arethen hydrogenated, preferably fully hydrogenated, to a CBC. Nonlimitingexamples of suitable CBC include CBC that is fully hydrogenated di-block(SB), tri-block (SBS) and penta-block (SBSBS) polymer. In such tri- andpenta-block copolymer, each block of a type of unit is the same length;i.e., each S block is the same length and each B block is the samelength. Total molecular weight (Mn) prior to hydrogenation is from about25,000 to about 1,000,000 g/mol. The percent of styrene incorporated isfrom 10 to 99 wt %, or from 50 to 95 wt % or from 80 to 90 wt %, thebalance being butadiene. For example, WO2000/056783(A1), incorporated byreference herein, discloses the preparation of such pentablock types ofCOPs.

Other COPs are described in Yamazaki, Journal of Molecular Catalysis A:Chemical, 213 (2004) 81-87; and Shin et al., Pure Appl. Chem., Vol. 77,No. 5, (2005) 801-814. In the publication from Yarnazaki (of ZeonChemical) the polymerization of a COP is described as based on a ringopening metathesis route via norbornene. Commercially available COPproducts from Zeon Chemical are described as an amorphous polyolefinwith a bulky ring structure in the main chain, based ondicyclopentadiene as the main monomer and saturating the double bond innorbornene ring-opening metathesis with a substituent (R) byhydrogenation. A nonlimiting example of a suitable is COP is Zeonor 1420sold by Zeon Chemical.

Another example of COPs are the Topas brand cyclic olefin copolymerscommercially available from Topas Advanced Polymers GmbH which areamorphous, transparent copolymers based on cyclic olefins (i.e.,norbornene) and linear olefins (e.g., ethylene), with heat propertiesbeing increased with higher cyclic olefin content. Preferably such COP sare represented by the following formula with the x and y valuesselected to provide suitable thermoplastic polymers:

The layers comprising the COPs can be made from COPs or can comprisephysical blends of two or more COPs and also physical blends of one ormore COP with polymers that are not COPs provided that any COP blends orcompositions comprise at least 25 wt % cyclic olefin unit content in thetotal blend or composition.

In an embodiment, layer B includes a cyclic block copolymer.

In an embodiment, layer B includes a cyclic block copolymer that is apentablock hydrogenated styrene.

In an embodiment, the multilayer film includes layer A having apropylene homopolymer with a T₁c less than 125° C. The propylenehomopolymer has a MFR from 1.5 g/10 min to 2.5 g/10 min. Thepropylene-based polymer has a crystallinity from 35% to 45%. Layer Bincludes a COP with a T₂g greater than 125° C., or greater than 130° C.,or greater than 135° C., or greater than 140° C. In a furtherembodiment, the (COP) T2g-T₁c (propylene homopolymer) is greater than10° C., or greater than 20° C.

C. Core Component

The core component of the present multilayer film includes from 15 to1000 alternating layers of layer A and layer B.

In an embodiment, the core component includes from 15, or 30, or 33, or50, or 60, or 65, or 70, or 100, or 129, or 145, or 150, or 200 to 250,or 257, or 300, or 400, or 450, or 500, or 1000 alternating layers oflayer A and layer B.

The thickness of layer A and layer B can be the same or different. In anembodiment, the thickness of layer A is the same, or substantially thesame, as the thickness of layer B. Layer A has a thickness from 10 nm,or 20 nm, or 30 nm, or 50 nm, or 70 nm, or 80 nm, or 100 nm, or 145 nm,or 150 nm, or 198 nm, or 200 nm, or 250 nm, or 290 nm, or 300 nm, or 350nm, or 396 nm, or 400 nm, or 450 nm to 500 nm, or 600 nm, or 700 nm, or792 nm, or 800 nm, or 900 nm, or 1000 nm. Layer B has a thickness from10 nm, or 20 nm, or 30 nm, or 50 nm, or 70 nm, or 80 nm, or 100 nm, or145 nm, or 150 nm, or 198 nm, or 200 nm, or 250 nm, or 290 nm, or 300nm, or 350 nm, or 396 nm, or 400 nm, or 450 nm to 500 nm, or 600 nm, or700 nm, or 792 nm, or 800 nm, or 900 nm, or 1000 nm.

The number of A layers and B layers present in the core component can bethe same or different. In an embodiment, the A:B layer ratio (number ofA layers to the number of B layers) is from 1:1, or 3:1, to 9:1.

In an embodiment, the core component includes 60 to 70, or 65alternating layers of layer A and layer B and the core component has anA:B layer ratio from 50:50, or 75:25 to 90:10. Layer A has a thicknessfrom 30 nm, or 100 nm, or 200 nm to 400 nm, or 500 nm.

The core component may be produced with a multilayer coextrusionapparatus as generally illustrated in FIG. 1. The feedblock for amulti-component multilayer system usually combines the polymericcomponents into a layered structure of the different componentmaterials. The starting layer thicknesses (their relative volumepercentages) are used to provide the desired relative thicknesses of theA and B layers in the final film.

The present core component is a two component structure composed ofpolymeric material “A” (produces layer A) and polymeric material “B”(produces layer B) and is initially coextruded into a starting “AB” or“ABA” layered feedstream configuration where “A” represents layer A and“B” represents layer B. Then, known layer multiplier techniques can beapplied to multiply and thin the layers resulting from the feedstream.Layer multiplication is usually performed by dividing the initial feedstream into 2 or more channels and “stacking” of the channels. Thegeneral formula for calculation of the total numbers of layers in amultilayer structure using a feedblock and repeated, identical layermultipliers is: n_(t)=(N_(I))(F)^(n) where: N_(t) is the total number oflayers in the final structure; N_(I) is the initial number of layersproduced by the feedblock; F is the number of layer multiplications in asingle layer multiplier, usually the “stacking” of 2 or more channels;and n is number of identical layer multiplications that are employed.

For multilayer structures of two component materials A and B, a threelayer ABA initial structure is frequently employed to result in a finalfilm or sheet where the outside layers are the same on both sides of thefilm or sheet after the layer multiplication step(s). Where the A and Blayers in the final film or sheet are intended to be generally equalthickness and equal volume percentages, the two A layers in the startingABA layer structure are half the thickness of the B layer but, whencombined together in layer multiplication, provide the same layerthickness (excepting the two, thinner outside layers) and comprise halfof the volume percentage-wise. As can be seen, since the layermultiplication process divides and stacks the starting structuremultiple times, two outside A layers are always combined each time thefeedstream is “stacked” and then add up to equal the B layer thickness.In general, the starting A and B layer thicknesses (relative volumepercentages) are used to provide the desired relative thicknesses of theA and B layers in the final film. Since the combination of two adjacent,like layers appears to produce only a single discrete layer for layercounting purposes, the general formula N_(t)=(2)^((n+1))+1 is used forcalculating the total numbers of “discrete” layers in a multilayerstructure using an “ABA” feedblock and repeated, identical layermultipliers where N_(t) is the total number of layers in the finalstructure; 3 initial layers are produced by the feedblock; a layermultiplication is division into and stacking of 2 channels; and n isnumber of identical layer multiplications that are employed.

A suitable two component coextrusion system (e.g., repetitions of “AB”or “ABA”) has two 3/4‘ inch (19.05 mm) single screw extruders connectedby a melt pump to a coextrusion feedblock. The melt pumps control thetwo melt streams that are combined in the feedblock as two or threeparallel layers in a multilayer feedstream. Adjusting the melt pumpspeed varies the relative layer volumes (thicknesses) and thus thethickness ratio of layer A to layer B. From the feedblock, thefeedstream melt goes through a series of multiplying elements. It isunderstood that the number of extruders used to pump melt streams to thefeedblock in the fabrication of the structures of the disclosuregenerally equals the number of different components. Thus, athree-component repeating segment in the multilayer structure (ABC . . .), requires three extruders.

Examples of known feedblock processes and technology are illustrated inWO 2008/008875; U.S. Pat. No. 3,565,985; U.S. Pat. No. 3,557,265; andU.S. Pat. No. 3,884,606, each of which is hereby incorporated byreference herein. Layer multiplication process steps are shown, forexample, in U.S. Pat. Nos. 5,094,788 and 5,094,793, hereby incorporatedherein by reference, teaching the formation of a multilayer flow streamby dividing a multilayer flow stream containing the thermoplasticresinous materials into first, second and optionally other substreamsand combining the multiple substreams in a stacking fashion andcompressing, thereby forming a multilayer flow stream. As may be neededdepending upon materials being employed for film or sheet production andthe film or sheet structures desired, films or sheet comprising 2 ormore layers of the multilayer flow stream can be provided byencapsulation techniques such as shown by U.S. Pat. No. 4,842,791encapsulating with one or more generally circular or rectangularencapsulating layers stacked around a core; as shown by of U.S. Pat. No.6,685,872 with a generally circular, nonuniform encapsulating layer;and/or as shown by WO 2010/096608A2 where encapsulated multilayeredfilms or sheet are produced in an annular die process. U.S. Pat. Nos.4,842,791 and 6,685,872 and WO 2010/096608A2 are hereby incorporated byreference herein.

In an embodiment, the core component includes from 15 to 1000alternating layers of layer A and layer B. Layer A has a thickness from30 nm, or 100 nm to 500 nm and includes the propylene-based polymer withT₁c as disclosed above. Layer B includes the second polymer, either apolycarbonate or a COP, with T₂g as disclosed above. Layer A has aneffective moisture permeability from 0.1 to less than 0.40 g-mil/100in²/day (from 1.55 to less than 6.2 g-mil/m²/24 hr).

In an embodiment, layer A of the core component includes a propylenehomopolymer with a T₁c less than 125° C. In a further embodiment, thepropylene homopolymer has a melt flow rate from 1.5 g/10 min to 2.5 g/10min. In yet a further embodiment, the propylene homopolymer has acrystallinity from 35% to 60%.

In an embodiment, the second polymer in the core component is selectedfrom a polycarbonate and a cyclic olefin polymer.

In an embodiment, layer A of the core component includes a propylenehomopolymer with a T₁c less than 125° C. and a melt flow rate from 1.5g/10 min to 2.5 g/10 min. Layer B includes a polycarbonate with a T₂ggreater than 125° C. In a further embodiment, the T₂g(polycarbonate)-T₁c (propylene homopolymer) is greater than 20° C.

In an embodiment, layer A has a thickness from 200 nm to 400 nm andlayer A includes the propylene homopolymer with T₁c less than 125° C. asdisclosed above. Layer B includes the polycarbonate with T₂g greaterthan 125° C. as disclosed above. Layer A has an effective moisturepermeability from 0.2 to less than or equal to 0.3 g-mil/100 in²/day(from 3.1 to less than or equal to 4.65 g-mil/m²/24 hr).

In an embodiment, the core component has layer A which includes thepropylene homopolymer with a T₁c less than 125° C. as disclosed above.Layer B includes a cyclic olefin polymer with a T₂g greater than 125° C.In a further embodiment, the T₂g (COP)-T₁c (propylene homopolymer) isgreater than 20° C. In yet a further embodiment, the cyclic olefinpolymer is a cyclic block copolymer.

In an embodiment, layer A has a thickness from 200 nm to 400 nm andlayer A includes the propylene homopolymer with T₁c less than 125° C. asdisclosed above. Layer B includes the a cyclic block copolymer with T₂ggreater than 125° C. as disclosed above. Layer A has an effectivemoisture permeability from 0.2 to less than or equal to 0.3 g-mil/100in²/day (from 3.1 to less than or equal to 4.65 g-mil/m²/24 hr).

In an embodiment, the core component has a total thickness from 0.1 mil(2.54 micrometers) to 10.0 mil (254 micrometers). In a furtherembodiment, the core component has a thickness from 0.1 mil, or 0.2 mil,or 0.3 mil, or 0.4 mil, or 0.5 mil, to 0.8 mil, or 1.0 mil, or 1.5 mil,or 2.0 mil, or 3.0 mil, or 5.0 mil, or 7.7 mil, or 10.0 mil.

The core component may comprise two or more embodiments disclosedherein.

D. Skin Layers

In an embodiment, the multilayer film includes at least one skin layer.In a further embodiment, the multilayer film includes two skin layers.The skin layers are outermost layers, with a skin layer on each side ofthe core component. The skin layers oppose each other and sandwich thecore component. The composition of each individual skin layer may be thesame or different as the other skin layer. Nonlimiting examples ofsuitable polymers that can be used as skin layers includepolypropylenes, polyethylene oxide, polycaprolactone, polyamides,polyesters, polyvinylidene fluoride, polystyrene, polycarbonate,polymethylmethacrylate, polyamides, ethylene-co-acrylic acid copolymers,polyoxymethylene and blends of two or more of these; and blends withother polymers comprising one or more of these.

In an embodiment, the skin layers include propylene-based polymer,ethylene-based polymer polyethylene, polyethylene copolymers,polypropylene, propylene copolymer, polyamide, polystyrene,polycarbonate and polyethylene-co-acrylic acid copolymers.

The thickness of each skin layer may be the same or different. The twoskin layers have a thickness from 5%, or 10%, or 15% to 20%, or 30%, or35% the total volume of multilayer film.

In an embodiment, the thickness of the skin layers is the same. The twoskin layers with the same thickness are present in multilayer film inthe volume percent set forth above. For example, a multilayer film with35% skin layer indicates each skin layer is present at 17.5% the totalvolume of the multilayer film.

In an embodiment, the composition of each skin layer is the same and isa propylene-based polymer. In a further embodiment, each skin layer issame propylene-based polymer as the propylene-based polymer that ispresent in layer A.

In an embodiment, each skin layer includes a propylene homopolymer. Thepropylene homopolymer for each skin layer has a MFR from 0.1 g/10 min,or 0.5 g/10 min, or 1.0 g/10 min, or 1.5 g/10 min, to 2.0 g/10 min, or2.5 g/10 min. The propylene homopolymer has a density from 0.85 g/cc to0.95 g/cc. The propylene homopolymer has a crystallization temperature(T₁c) less than 125° C., or from 115° C., or 118° C., or 120° C., or122° C. to less than 125° C. The propylene homopolymer has a meltingtemperature, Tm, from 155° C., or 160° C. to 165° C., or 170° C. Thepropylene homopolymer has a crystallinity from 30%, or 35%, or 38% to40% to 45%, or 50%, or 55%, or 60%.

E. Optional Other Layer

The skin layers may be in direct contact with the core component (nointervening layers). Alternatively, the multilayer film may include oneor more intervening layers between each skin layer and the corecomponent. The present multilayer film may include optional additionallayers. The optional layer(s) may be intervening layers (or internallayers) located between the core component and the skin layer(s). Suchintervening layers (or internal layers) may be single, repeating, orregularly repeating layer(s). Such optional layers can include thematerials that have (or provide) sufficient adhesion and provide desiredproperties to the films or sheet, such as tie layers, barrier layers,skin layers, etc.

Nonlimiting examples of suitable polymers that can be employed as tie oradhesive layers include: olefin block copolymers such as propylene-basedblock copolymer sold under the Tradename INTUNE™ (The Dow ChemicalCompany) and ethylene-based block copolymer sold under the TradenameINFUSE™ (The Dow Chemical Company); polar ethylene copolymers such ascopolymers with vinyl acetate; acrylic acid, methyl acrylate, and ethylacrylate; ionomers; maleic anhydride-grafted ethylene polymers andcopolymers; blends of two or more of these; and blends with otherpolymers comprising one or more of these.

Nonlimiting examples of suitable polymers that can be employed asbarrier layers include: polyethylene terephthalate, ethylene vinylalcohol, polyvinylidene chloride copolymers, polyamides, polyketones,MXD6 nylon, blends of two or more of these; and blends with otherpolymers comprising one or more of these.

As noted above, the multilayer film according to the present disclosurecan be advantageously employed as a component in thicker structureshaving other inner layers that provide structure or other properties inthe final article. For example, the skin layers can be selected to havean additional desirable properties such as toughness, printability andthe like are advantageously employed on either side of the corecomponent to provide films suitable for packaging and many otherapplications where their combinations of moisture barrier, gas barrier,physical properties and low cost will be well suited. In another aspectof the present disclosure, tie layers can be used with the multilayerfilm or sheet structures according to the present disclosure.

F. Multilayer Films

The multilayer film of the present disclosure can be a stand-alone filmor can be a component of another film, a laminate, a sheet, or anarticle.

The present multilayer film may be used as films or sheets for variousknown film or sheet applications or as layers in thicker structures andto maintain light weight and low costs.

When employed in this way in a laminate structure or article with outersurface or skin layers and optional other inner layers, the presentmultilayer film can be used to provide at least 5 volume % of adesirable film or sheet, including in the form of a profile, tube,parison or other laminate article, the balance of which is made up by upto 95 volume % of additional outer surface or skin layers and/or innerlayers.

In an embodiment, the present multilayer film provides at least 10volume %, or at least 15 volume %, or at least 20 volume %, or at least25 volume %, or at least 30 volume % of a laminate article.

In an embodiment, the present multilayer film provides up to 100 volume%, or less than 80 volume %, or less than 70 volume %, or less than 60volume %, or less than 50 volume %.

For nanolayer structures, two relationships exist which influenceharrier property—(i) crystal lamella orientation and (ii) %crystallinity. It is known that the thinner the nanolayer becomes, themorphology moves from spherulitic with an overall random orientation oflamellae but containing some of which are in the edge-on orientation, toin-plane lamellae. However, orientation is inversely related tocrystallinity, such that as confinement increases (barrier becomesthinner), the degree of crystallinity for the barrier polymer decreases,reducing barrier capability. Moreover, many barrier resins do not form“in-plane” lamellae crystals upon confinement and only drop %crystallinity, and thus deteriorate the barrier property. Therefore, formany barrier materials, it is necessary to maintain overall %crystallinity as high as possible and reduce the portions of “edge-on”lamellae in the spherulitic crystals.

Bounded by no particular theory, Applicant discovered that creation oftruncated spherulites in nanolayer structures unexpectedly optimizesbarrier capability. With (1) control of layer thickness and (2)selection of barrier and constraining components, nanolayer withtruncated spherulite morphology can be obtained which exhibit unexpectedimprovement in moisture permeability.

A “spherulite” is a superstructure observed in many semi-crystallinepolymers and is composed of branched crystal lamella radiating from acentral nucleation point. If spherulite growth is not confined, thespherulite grows in the radial direction symmetrically as a sphere untilit impinges on other spherulites. The lamella direction in thespherulite is, on average, random. A “truncated spherulite” is aspherulite that is confined in at least one dimension by the thicknessof the film from which it is grown. If the film is grown in thehorizontal plane, growth is terminated at the top and the bottom(perpendicular to horizontal plane) while growth more parallel to thefilm continues as in the unconfined example, until another spherulite(also truncated by the constraining layer) is encountered. The truncatedspherulite is not symmetric and the lamella orientation is, on average,no longer random. A truncated spherulite is formed by eliminating a topportion and a bottom portion of the spherulite with opposingconstraining layers. A truncated spherulite has lamella with a moreperpendicular component to its direction, relative to the horizontalplane of the film.

Bounded by no particular theory, Applicant discovered that creation oftruncated spherulites in nanolayer structures unexpectedly optimizesbarrier capability. With (1) control of layer thickness and (2)selection of barrier and constraining components, nanolayer withtruncated spherulite orientation can be obtained which exhibitunexpected improvement in both effective moisture permeability andeffective oxygen permeability.

As a benchmark, polyethylene oxide (PEO) barrier shows a relationship ofstarting at a low permeation rate with the thinnest layers due toin-plane crystal lamella, and then rising to the permeation rate of bulkpolymer as layer thickness increases.

In contrast, for polyethylene it is known that at small layer thicknessin nanolayer film, edge-on crystal lamella are present which do notyield a decrease in permeation rate over that of the bulk. See forexample Pan et al, J. Polym. Sci., Polym. Phys., 28 1105 (1990).

Applicant unexpectedly discovered and created a nanolayer configurationwhereby propylene-based polymer (and propylene homopolymer inparticular) exhibits an optimal permeation rate with layer thicknessfrom 30 nm to 1000 nm and 100 nm to 500 nm in particular.

The propylene-based polymer (barrier polymer layer A) creates “edge-on”lamellae structure due to an active surface (interface) nucleation whenthe propylene-based polymer is constrained by polycarbonate or COP(layer B). Applicant discovered, that at optimal layer thickness (100 nmto 500 nm), the edge-on portions of the lamellae structure are removed(or truncated) from the spherulites, leaving the remaining portion ofthe spherulitic structure without a reduction in crystallinity.Applicant's truncated spherulitic structure increases the ratio of“in-plane” lamellae (good for barrier) to “edge-on” lamellae (poor forbarrier) compared to random oriented lamellae structure (snowflake) inan unconstrained system. This truncated spherulitic structureunexpectedly finds a balance between orientation and crystallinity andexhibits a synergistic improvement in both effective moisturepermeability and effective oxygen permeability.

G. Article

The present disclosure, provides an article. In an embodiment, thepresent multilayer film is a component of an article. Nonlimitingexamples of suitable articles include laminate structures, die formedarticles, thermoformed articles, vacuum formed articles, or pressureformed articles. Other articles include tubes, parisons, and blow moldedarticles such as bottles or other containers.

Test Methods

Percent crystallinity, melting temperature, Tm, crystallizationtemperature (Tc), and glass transition temperature (Tg), each ismeasured by way of Differential Scanning calorimerty (DSC) as set forthbelow.

DSC

Differential Scanning calorimetry (DSC) can be used to measure themelting, crystallization, and glass transition behavior of a polymerover a wide range of temperature. For example, the TA Instruments Q1000DSC, equipped with an RCS (refrigerated cooling system) and anautosampler is used to perform this analysis. During testing, a nitrogenpurge gas flow of 50 ml/min is used. Each sample is melt pressed into athin film at about 175° C.; the melted sample is then air-cooled to roomtemperature (about 25° C.). A 3-10 mg, 6 mm diameter specimen isextracted from the cooled polymer, weighed, placed in a light aluminumpan (ca 50 mg), and crimped shut. Analysis is then performed todetermine its thermal properties.

The thermal behavior of the sample is determined by ramping the sampletemperature up and down to create a heat flow versus temperatureprofile. First, the sample is rapidly heated to 180° C. and heldisothermal for 3 minutes in order to remove its thermal history. Next,the sample is cooled to −40° C. at a 10° C./minute cooling rate and heldisothermal at −40° C. for 3 minutes. The sample is then heated to 180°C. (this is the “second heat” ramp) at a 10° C./minute heating rate. Thecooling and second heating curves are recorded. The cool curve isanalyzed by setting baseline endpoints from the beginning ofcrystallization to −20° C. The heat curve is analyzed by settingbaseline endpoints from −20° C. to the end of melt. The valuesdetermined are extrapolated onset of melting, Tm, and extrapolated onsetof crystallization, Tc. Heat of fusion (H_(f)) (in Joules per gram), andthe calculated % crystallinity for polyethylene samples using theEquation below:

Crystallinity=((H _(f))/292 J/g)×100

The heat of fusion (H_(f)) and the peak melting temperature are reportedfrom the second heat curve. Peak crystallization temperature isdetermined from the cooling curve.

Melting point, Tm, is determined from the DSC heating curve by firstdrawing the baseline between the start and end of the meltingtransition. A tangent line is then drawn to the data on the lowtemperature side of the melting peak. Where this line intersects thebaseline is the extrapolated onset of melting (Tm). This is as describedin B. Wunderlich in Thermal Characterization of Polymeric Materials,2^(nd) edition, Academic Press, 1997, E. Turi ed., pgs 277 and 278.

Crystallization temperature, Tc, is determined from a DSC cooling curveas above except the tangent line is drawn on the high temperature sideof the crystallization peak. Where this tangent intersects the baselineis the extrapolated onset of crystallization (Tc).

Glass transition temperature, Tg, is determined from the DSC heatingcurve where half the sample has gained the liquid heat capacity asdescribed in B. Wunderlich in Thermal Characterization of PolymericMaterials, 2^(nd) edition, Academic Press, 1997, E. Turi ed., pg 278 and279. Baselines are drawn from below and above the glass transitionregion and extrapolated through the Tg region. The temperature at whichthe sample heat capacity is half-way between these baselines is the Tg.

Density is measured in accordance with ASTM D 792.

Effective permeability (Peff). The effective permeability (moisture andoxygen) for an individual barrier layer is calculated using Equation (1)as follows:

$\begin{matrix}{P_{B} = {V_{B}\left( {\frac{1}{P} - \frac{1 - V_{B}}{P_{c}}} \right)}^{- 1}} & {{Equation}\mspace{14mu} I}\end{matrix}$

wherein P is the permeability of the nanolayer component,V_(B) and V_(C)are the volume fraction of the barrier and confining polymers,respectively, and P_(B) and P_(C) are the permeability of the barrierand confining polymers, respectively. Effective moisture permeability ismeasured as g-mil/100 inch² (in²)/day and g-mil/meter² (m²)/24 hour(hr).

Melt flow rate (MFR) is measured 1 accordance with ASTM D 1238,Condition 280° C./2.16 kg (g/10 minutes).

Melt index (MI) is measured in accordance with ASTM D 1238, Condition190° C./2.16 kg (g/10 minutes).

Moisture permeability is a normalized calculation performed by firstmeasuring Water Vapor Transmission Rate (WVTR) for a given filmthickness. WVTR is measured at 38° C., 100% relative humidity and 1 atmpressure are measured with a MOCON Permatran-W 3/31. The instrument iscalibrated with National Institute of Standards and Technology certified25 μm-thick polyester film of known water vapor transportcharacteristics. The specimens are prepared and the WVTR is performedaccording to ASTM F 1249.

Oxygen permeability is a normalized calculation performed by firstmeasuring Oxygen Transmission Rate (OTR) for a given film thickness. OTRis measured at 23° C., 0% relative humidity and 1 atm pressure aremeasured with a MOCON OX-IRAN 2/20. The instrument is calibrated withNational Institute of Standards and Technology certified Mylar film ofknown O₂ transport characteristics. The specimens are prepared and theOTR is performed according to ASTM D 3985. Some embodiments of thepresent disclosure will now be described in detail in the followingExamples.

EXAMPLES

In the present examples, experimental films according to the presentdisclosure (unless noted to be “controls”) are prepared frompropylene-based polymer barrier layers (i.e., propylene homopolymer)coextruded with polycarbonate or cyclic olefin polymer constraininglayer.

Table 1 summarizes the propylene-based polymer materials giving tradename, density, Tc, Tm, and MFR. The propylene-based polymer materialPP1572 is commercially available from ExxonMobil.

TABLE 1 Propylene-based polymer MFR Propylene- Trade Density Tc Tm (g/10min) @ Moisture based polymer Name (g/cc) (° C.) (° C.) 230° C./2.16 kg% crystallinity permeability Propylene PP1572 0.90 118 162 2.1 ~40 0.5+homopolymer (7.75*) (PP1) +Moisture permeability-g-mil/100 in²/day*g-mil/m²/24 hr

Table 2 summarizes the polycarbonate. The polycarbonate is APEC 1745 andis commercially available from Bayer.

TABLE 2 Polycarbonate polymer MFR Trade Density Tg (g/10 min) @ MoisturePolycarbonate Name (g/cc) (° C.) 230° C./2.16 kg % crystallinitypermeability PC1 APEC 1.17 172 17.0 NA 16.5+ 1745 (225.75*) +Moisturepermeability-g-mil/100 in²/day *g-mil/m²/24 hr

Table 3 summarizes the COP materials giving trade name, density, cyclicunit, weight percentage of the cyclic units, control film. The COPmaterial HP030 is commercially available from Taiwan Rubber Company.

TABLE 3 COP Wt % MFR Cyclic Trade Density (g/10 min) @ Cyclic OlefinOlefin Moisture COP Name (g/cc) 280° C./2.16 kg Unit Unit permeabilityCyclic HP030 0.941 39 Pentablock >40% 1.1+ Block Hydrogenated (17.05*)Copolymer Styrene 1 (CBC1) +Moisture permeability-g-mil/100 in²/day*g-mil/m²/24 hr

Experimental films are prepared having 33, 65, 129 and 257 thin layersof alternating PP1 (barrier layer) and either PC1 or CBC1 (constraininglayer) where the resulting final layer thicknesses provided by the finalthicknesses to which the films are drawn down to. The nominal filmthickness (“Nom. Film Thickness”), nominal PP1 layer thickness, nominalconstraining layer thickness and total skin layer volume percentage(includes both skin layers) are given in Tables 4A-4C and 5A-5B below.The present multilayer film is made by a feedblock process as previouslydescribed and shown in FIG. 1.

The core component is made with A polymer (PP1) and B polymer(constraining layer PC1 or CBC1), and is extruded by two ¾ inch (19.05mm) single screw extruders connected by a melt pump to a coextrusionfeedblock with an BAB feedblock configuration (as described above). Themelt pumps control the two melt streams that are combined in thefeedblock; by adjusting the melt pump speed, the relative layerthickness, that is, the ratio of A to B can be varied. The feedblockprovides a feedstream to the layer multipliers as 3 parallel layers in aBAB configuration with B split into equal thicknesses of B layer oneither side of A layer in the total A:B volume ratios shown in thetables. Then, seven layer multiplications are employed, each dividingthe stream into 2 channels and stacking them to provide a final filmhaving 33, 65, 129, or 257 alternating discrete microlayers. Skin layersof PP1 that are about 34 or 50 volume percent of the final film areprovided to each surface (17 or 25 vol % to each side of the film) by anadditional extruder.

The extruders, multipliers and die temperatures are set to 240° C. forall the streams and layers of the multilayer products to ensure matchingviscosities of the two polymer melts. The multilayer extrudate isextruded from a flat 14 inch (35.5 cm) die having a die gap of 20 milsto a chill roll having a temperature of 80° C. with almost no air gapbetween the die and chill roll and providing a relatively fast coolingof the film. The overall flow rate is about 3 lbs/hr (1.36 kg/hr).

Embedded films are microtomed through the thickness at −75° C. with acryo-ultramicrotome (MT6000-XL from RMC) and cross-sections are examinedwith an atomic force microscope (AFM) to visualize the layers and themorphology inside layers. Phase and height images or the cross-sectionare recorded simultaneously at ambient temperature in air using thetapping mode of the Nanoscope IIIa MultiMode scanning probe (DigitalInstruments). Although there is some non-uniformity, the average layerthickness is observed to be quite close to the nominal layer thicknesscalculated from the film thickness, the composition ratio and the totalnumber of layers.

A control film (1 mil, 25 micron) is extruded from PP1, resin and testedas described below for control effective moisture permeability values.

TABLE 4A PP (Tc~118° C.) is constrained PP1/PC1 by PC (Tg~172° C.)Moisture+ Material Tm/Tg Tc Crystallinity % permeability PP1 1572 162118 ~40 0.50 ± 0.01 Control (7.75*) (1 mil) PC1 control 172 / / 16.5 (1mil) (225.75*) +g-mil/100 in2/day *g-mil/m2/24 hr

Table 4A, 4B, 4C—Peff, Moisture Permeability for PP1/PC1

TABLE 4B Nominal PP1 PP1 overall layer thickness Moisture Barrier %Crystallinity composition (nm) Peff+ in PP Sample info (PP1/PC1) 99 0.3738 257 layer, PP1[PP1/PC1]PP1 = 83/17 (5.74*) 17[49.5/16.5]17 145 0.3738 129 layer, PP1[PP1/PC1]PP1 = 87.5/12.5 (5.74*) 25[37.5/12.5]25 1980.35 39 129 layer, PP1[PP1/PC1]PP1 = 83/17 (5.42*) 17[49.5/16.5]17 2900.26 39 65 layer, PP1[PP1/PC1]PP1 = 87.5/12.5 (4.03*) 25[37.5/12.5]25396 0.3 39 65 layer, PP1[PP1/PC1]PP1 = 83/17 (4.65*) 17[49.5/16.5]17 5800.32 38 33 layer, PP1[PP1/PC1]PP1 = 87.5/12.5 (4.96*) 25[37.5/12.5]25792 0.35 39 33 layer, PP1[PP1/PC1]PP1 = 83/17 (5.42*) 17[49.5/16.5]17+Peff-PP1 moisture barrier (g-mil/100 in²/day) *g-mil/m²/24 hr

TABLE 4C When PP1 layer thickness is 290 nm, the calculated PP1 layershows~2X improvement in moisture permeability compared to the PP1control. After post extrusion stretching (draw ratio 2 × 2 @ 150 C.),PP1 control, Peff = 0.35 g.mil/100 in²/day Nominal PP1 PP1 layerMoisture overall thickness Barrier composition (nm) Peff+ Sample info(PP1/PC1) 99 0.23 257 layer, PP1[PP1/PC1]PP1 = 83/17 (3.56*)17[49.5/16.5]17 145 0.23 129 layer, PP1[PP1/PC1]PP1 = 87.5/12.5 (3.56*)25[37.5/12.5]25 198 0.2 129 layer, PP1[PP1/PC1]PP1 = 83/17 (3.1*)17[49.5/16.5]17 290 0.12 65 layer, PP1[PP1/PC1]PP1 = 87.5/12.5 (1.86*)25[37.5/12.5]25 396 0.16 65 layer, PP1[PP1/PC1]PP1 = 83/17 (2.48*)17[49.5/16.5]17 580 0.2 33 layer, PP1[PP1/PC1]PP1 = 87.5/12.5 (3.1*)25[37.5/12.5]25 792 0.21 33 layer, PP1[PP1/PC1]PP1 = 83/17 (3.2*)17[49.5/16.5]17 +Peff-Moisture barrier-PP1 (g-mil/100 in²/day)*g-mil/m²/24 hr

Table 5A and 5B—Peff for PP1/CBC1

TABLE 5A PP1 (Tc~118° C.) is constrained by CBC1 (Tg~143° C.) PP1/CBC1Nominal PP1 PP1 layer Moisture overall thickness Barrier composition(nm) Peff+ Sample info (PP1/CBC1) 99 0.32 257 layer, PP1[PP1/CBC1]PP1 =87.5/12.5 (4.96*) 17[49.5/16.5]17 145 0.31 129 layer, PP1[PP1/CBC1]PP1 =87.5/12.5 (4.80*) 25[37.5/12.5]25 290 0.22 65 layer, PP1[PP1/CBC1]PP1 =87.5/12.5 (3.41*) 25[37.5/12.5]25 580 0.31 33 layer, PP1[PP1/CBC1]PP1 =87.5/12.5 (4.80*) 25[37.5/12.5]25 +Peff-Moisture barrier-PP1 (g-mil/100in²/day) *g-mil/m²/24 hr

When PP layer thickness is 290 nm, the normalized PP layer moisturepermeability showed ˜2× improvement compared to extruded PP control.

TABLE 5B After post extrusion stretching (draw ratio 4 × 4 @ 150 C.),PP1 control = 0.16 g.mil/100 in²/day Nominal Moisture PP1 Barrier layerPeff, PP1 overall thickness (g-mil/ composition (nm) 100 in²/day) Sampleinfo (PP1/CBC1) 163 0.12 65 layer, PP1[PP1/CBC1]PP1 = 87.5/12.5 (1.86*)25[37.5/12.5]25 After stretch, the improvement is ~4X compared toextruded PP1 control. *g-mil/m²/24 hr

Peff calculation for moisture permeability (g-mil/100 in²/day):

${{Peff}\mspace{14mu} {barrier}\mspace{14mu} {polymer}} = {P_{B} = {V_{B}\left( {\frac{1}{P} - \frac{1 - V_{B}}{P_{c}}} \right)}^{- 1}}$

This equation can be extended to 3 material system (barrier polymer,confining polymer, and skin material as:

$P_{{eff},{PP}} = {V_{P\; P}\left( {\frac{1}{P} - \frac{V_{c}}{P_{c}} - \frac{V_{skin}}{P_{skin}}} \right)}^{- 1}$

Moisture permeability calculation:

$P = \left( {\frac{\varnothing_{A}}{P_{A}} + \frac{1 - \varnothing_{A}}{P_{B}}} \right)^{- 1}$

This equation can be extended to 3 material system as well:

$P = \left( {\frac{\varnothing_{B}}{P_{B}} + \frac{\varnothing_{C}}{P_{C}} + \frac{\varnothing_{skin}}{P_{skin}}} \right)^{- 1}$

Moisture permeability

-   A. Calculation for 290 nm thick PP1 (barrier) and CBC1    (constraining) Example in Table 5A (PP1/CBC1 case)    -   (1) Measured moisture permeability=0.35    -   (2) Calculation for Peff:Peff,        PP1=0.375(1/0.35−0.125/1.1−0.5/0.5)̂−1=0.22 (input values: volume        of PP1 in the microlayer core=0.375 (37.5%), overall film        moisture permeability (measured)=0.35, volume of CBC1=0.125,        CBC1 permeability=1.1, volume of PP1 skin=0.5, and skin PP1        permeability=0.5)-   B. Calculation for 290 nm thick PP1 (barrier) and PC1 (constraining)    Example in Table 4B(PP1/PC1 case)    -   (1) Measured moisture permeability=0.40    -   (2) Calculation for Peff:Peff,        PP1=0.375(1/0.40−0.125/16.5−0.5/0.5)̂−1=0.26 (input values:        volume of PP1 in the microlayer core=0.375 (37.5%), overall film        moisture permeability (measured)=0.40, volume of PC1=0.125, PC1        permeability=16.5, volume of PP1 skin=0.5, and skin PP1        permeability=0.5)

The series model can be expanded as shown below to accommodate as manycomponents as needed:

$\frac{1}{P} = {\frac{\varnothing_{1}}{P_{1}} + \frac{\varnothing_{2}}{P_{2}} + {\frac{\varnothing_{3}}{P_{3}}\; \ldots}}$

-   -   Where P=the measured permeability of the multilayer film.        -   Φ_(i)= the volume fraction of the polymer i        -   P_(i)= permeability of polymer i

Applicant discovered that 100 nm to 500 nm PP1 barrier with truncatedspherulitic structure exhibits an unexpected drop (i.e., improvedbarrier properties) in effective moisture permeability. The effectivemoisture permeability improved by ˜2× by microlayering and ˜4× afterstretching over control.

It is specifically intended that the present disclosure not be limitedto the embodiments and illustrations contained herein, but includemodified forms of those embodiments including portions of theembodiments and combinations of elements of different embodiments ascome within the scope of the following claims.

1. A coextruded multilayer film comprising: a core component comprisingfrom 15 to 1000 alternating layers of layer A and layer B; layer Ahaving a thickness from 100 nm to 500 nm and comprising apropylene-based polymer having a crystallization temperature (T₁c);layer B comprising a second polymer having a glass transitiontemperature (T₂g), wherein T₁c<T₂g; and layer A has an effectivemoisture permeability from 1.55 g-mil/m²/24 hr to less than or equal to4.65 g-mil/m²/24 hr.
 2. The multilayer film of claim 1 wherein layer Ahas a thickness from 200 nm to 400 nm.
 3. The multilayer film of claim 1wherein layer A comprises a propylene homopolymer with a T₁c less than125° C.
 4. The multilayer film of claim 1 wherein the propylenehomopolymer has a melt flow rate from 1.5 g/10 min to 2.5 g/10 min. 5.The multilayer film of claim 1 wherein the propylene homopolymer has acrystallinity from 35% to 60%.
 6. The multilayer film of claim 1 whereinthe second polymer is selected from the group consisting of apolycarbonate and a cyclic olefin polymer.
 7. The multilayer film ofclaim 1 wherein layer A comprises a propylene homopolymer with a T₁cless than 125° C. and a melt flow rate from 1.5 g/10 min to 2.5 g/10min; and layer B comprises a polycarbonate with a T₂g greater than 125°C.
 8. The multilayer film of claim 1 wherein T₂g-T₁c is greater than 20°C.
 9. The multilayer film of claim 1 wherein layer A has a thicknessfrom 200 nm to 400 nm and layer A has an effective moisture permeabilityfrom 3.1 g-mil/m²/24 hr to less than or equal to 4.65 g-mil/m²/24 hr.10. The multilayer film of claim 1 wherein layer A comprises a propylenehomopolymer with a T₁c less than 125° C.; and layer B comprises a cyclicolefin polymer with a T₂g greater than 125° C.
 11. The multilayer filmof claim 10 wherein T₂g-T₁c is greater than 20° C.
 12. The multilayerfilm of claim 10 wherein the cyclic olefin polymer is a cyclic blockcopolymer.
 13. The multilayer film of claim 12 wherein the cyclic blockcopolymer comprises a pentablock hydrogenated styrene.
 14. Themultilayer film of claim 10 wherein layer A has a thickness from 200 nmto 400 nm and layer A has an effective moisture permeability from 3.1g-mil/m²/24 hr to less than or equal to 4.65 g-mil/m²/24 hr.
 15. Themultilayer film of claim 1 wherein the core component has a thicknessfrom 0.1 mil to 10.0 mil.
 16. The multilayer film of claim 1 comprisingat least one skin layer.
 17. The multilayer film of claim 16 wherein theskin layers comprise a propylene-based polymer.